White spot puts prawn farms in crosshairs

Queensland prawn farmer Elwyn Truloff has lost $4 million and his life's work to an outbreak of white spot disease.

But he says his losses will pale in comparison to the "disaster" that will unfold if the virus gets away and infects more farms and wild prawn fisheries in Australia.

Biosecurity officials are scrambling to contain the disease after it was detected in prawns taken from the Logan River in the state's southeast and at three of eight land-based prawn farms in the area.

Just two of Mr Truloff's 25 ponds have returned positive tests, but authorities are using huge amounts of chlorine to kill every prawn on all three infected farms in a bid to halt the disease's spread.

Mr Truloff's dire warning of impending disaster might seem an overstatement until you read what it's done to farmed prawn production overseas.

White spot was first detected in China's Fujian province in 1992. By the following year, it was in Japan and Thailand, and not long afterwards, the US, central and south America, and then France and Iran.

At its peak in China, outbreaks slashed total farmed prawn production by a staggering 80 per cent.

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In the mid-1990s, the value of prawn production in Thailand alone fell by $US500 million.

CSIRO virologist Jeff Cowley says the pressure is on to contain the disease to the Logan region, and establish the entry path for a virus that also infects other crustaceans.

The virus poses no risk to humans, but can have a high mortality rate in the host species it infects.

Rightly or wrongly, some farmers including Mr Truloff are blaming infected green prawns, imported from overseas, for white spot's arrival in Australia despite a testing regime designed to prevent that.

"Now we've got it here, it's come from the river into the prawn ponds. Now they've got the biggest problem in history, of ever getting rid of it," he told 4BC radio in an emotional interview.

"If it gets out in the bay ... like it did out in Thailand, in Taiwan, it'll move along the coast ... it's going to be the biggest disaster in history."

In April 2010, Biosecurity Australia introduced new quarantine rules for imported green prawns and prawn products after white spot was identified as a key risk.

The new rules required lab tests on samples from all consignments before they could be released and sold for human consumption.

Dr Cowley said other changes - such as mandating the removal of heads and shells - were clearly aimed at dissuading anglers from using imported green prawns bought at the supermarket as bait.

He said an exhaustive investigation would determine if imported prawns had any link to the Logan outbreak.

But Dr Cowley added it was certainly a possibility that infected prawns may not have been detected by the testing regime.

"It is possible to have an infected prawn used as bait potentially infecting a crab or a prawn," he said.